#include <stdlib.h>
#include <stdint.h>
#include <stddef.h>
#include <assert.h>
#include <string.h>

#include "circ_buff.h"

// Defines the circular buffer structure
struct circ_buf_t {
	char** buffer;
	size_t head;
	size_t tail;
	size_t max; // of the buffer
	bool full;
};

// Private Functions

static void advance_pointer(cbuf_handle_t cbuf) {
	assert(cbuf);

	if(cbuf->full) {
		cbuf->tail = (cbuf->tail + 1) % cbuf->max;
	}

	cbuf->head = (cbuf->head + 1) % cbuf->max;

	// We mark full because we will advance tail on the next time around
	cbuf->full = (cbuf->head == cbuf->tail);
}

static void retreat_pointer(cbuf_handle_t cbuf) {
	assert(cbuf);

	cbuf->full = false;
	cbuf->tail = (cbuf->tail + 1) % cbuf->max;
}

// APIs

cbuf_handle_t circ_buf_init(char** buffer, size_t size) {
	assert(buffer && size);

	cbuf_handle_t cbuf = malloc(sizeof(circ_buf_t));
	assert(cbuf);

	cbuf->buffer = buffer;
	cbuf->max = size;
	circ_buf_reset(cbuf);

	assert(circ_buf_empty(cbuf));

	return cbuf;
}

void circ_buf_free(cbuf_handle_t cbuf) {
	assert(cbuf);
	free(cbuf);
}

void circ_buf_reset(cbuf_handle_t cbuf) {
	assert(cbuf);

	cbuf->head = 0;
	cbuf->tail = 0;
	cbuf->full = false;
}

size_t circ_buf_size(cbuf_handle_t cbuf) {
	assert(cbuf);

	size_t size = cbuf->max;

	if(!cbuf->full) {
		if(cbuf->head >= cbuf->tail) {
			size = (cbuf->head - cbuf->tail);
		}
		else {
			size = (cbuf->max + cbuf->head - cbuf->tail);
		}
	}

	return size;
}

size_t circ_buf_capacity(cbuf_handle_t cbuf) {
	assert(cbuf);

	return cbuf->max;
}

void circ_buf_put(cbuf_handle_t cbuf, char data) {
	assert(cbuf && cbuf->buffer);

	strcpy(cbuf->buffer[cbuf->head], data);

	advance_pointer(cbuf);
}

int circ_buf_get(cbuf_handle_t cbuf, char* data) {
	assert(cbuf && data && cbuf->buffer);

	int r = -1;

	if(!circ_buf_empty(cbuf)) {
		strcpy(data, cbuf->buffer[cbuf->tail]);
		retreat_pointer(cbuf);

		r = 0;
	}

	return r;
}

bool circ_buf_empty(cbuf_handle_t cbuf) {
	assert(cbuf);

	return (!cbuf->full && (cbuf->head == cbuf->tail));
}

bool circ_buf_full(cbuf_handle_t cbuf) {
	assert(cbuf);

	return cbuf->full;
}